Long-Term Outcomes Following Radiotherapy for Pediatric Salivary Gland Tumors.

Abstract

Background: In contrast to adult salivary gland tumors, our institutional guidelines utilize lower radiation doses, smaller target margins, and proton therapy (PT) to minimize radiation to children's developing skull base anatomy. Herein, we report outcomes of our pediatric management approach.

Procedures: We identified 31 pediatric patients with salivary gland tumors treated with PT at our institution between 2006 and 2023. Most common histologies were mucoepidermoid carcinoma (n = 14), acinic cell carcinoma (n = 5), and adenoid cystic carcinoma (n = 5). Eight patients with radiographic lymphadenopathy underwent neck dissection prior to presentation, with selective dissections involving <4 nodal levels in 7/8 cases. The gross tumor volume (GTV) encompassed the residual tumor and tumor bed. Clinical target volume (CTV1), defined as GTV + 1 cm margin, received 50.4 Gy. Prophylactic nodal irradiation was administered to three patients. CTV2 equaled the GTV and was treated to a median total dose of 64.8 Gy (range, 61.2-70.8). Toxicity was assessed with CTCAE Version 5.0.

Results: Median follow-up was 7.5 years (range, 1.2-15). Overall survival (OS) was 96%, and local control was 94%. There were no nodal recurrences. Acute toxicities were limited to mucositis requiring opioids and transient Grade 3 dermatitis. The most serious late toxicity involved the auditory system, including three patients requiring hearing aids, one with chronic otitis media, one with osteonecrosis of the mastoid, and one with external canal stenosis. There was neither Grade 4 toxicity nor second malignancy.

Conclusions: Conservative neck management and moderate-dose PT delivered to smaller volumes resulted in excellent long-term disease control and limited toxicity in children with common salivary gland tumors.